There is an on-going need for measuring the content of drilling fluids, also known as drilling muds or drill muds. There may be a need to measure the content of fluid returning from the drill head, carrying sediment, or alternatively to measure the content of fluid sent to the drill head.
A method of measuring drilling fluids using X-ray fluorescence, XRF, is proposed in WO 1993/017326. However, this document is silent as to the experimental details of obtaining reproducible measurements from drilling fluids.
The reason this is important is that quantitative X-ray fluorescence is a technique that obtains data that is very highly dependent on the exact positions and orientations of the X-ray source, X-ray detector and sample. Even small deviations in distance between source and sample or between detector and sample can result in significant changes in the strength of X-ray fluorescence signals. For solid samples, it is less difficult to arrange for source, detector and sample to be in a very precisely known and reproducible position. There remains however a need to achieve the same accuracy with fluid samples.
An X-ray head used for measuring slurries (or liquids) is proposed in U.S. Pat. No. 3,354,308. Slurries are pumped through an inner pipe with an open end terminating in a larger pipe. A membrane closes off the larger pipe and X-ray measurements are made through the membrane using an X-ray source and a pair of X-ray detectors. However, there is no control of the exact position of the upper surface of the slurry which can vary, for example with changing composition, temperature or viscosity of the slurry and further the membrane can in some cases influence the measured results.